Final answer:
Informal institutions include culture, ethics and norms. These institutions are not written rules, but rather unwritten understandings and expectations that guide behavior.
Step-by-step explanation:
Informal institutions include culture, ethics, and norms.
These institutions are not written rules, but rather unwritten understandings and expectations that guide behavior. For example, social norms dictate how people should behave in certain situations, such as saying 'please' and 'thank you.'